1. Field of the Invention
The present invention relates generally to personal audio devices such as headphones that include adaptive noise cancellation (ANC), and, more specifically, to architectural features of an ANC system in which leakage from an earspeaker to the reference microphone is modeled.
2. Background of the Invention
Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as MP3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise canceling using a reference microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
When the acoustic path from the transducer to the reference microphone is not highly attenuative, for example when the transducer and reference microphone are included on an earspeaker, or when a telephone-mounted output transducer is not pressed to the user's ear, the ANC system will try to cancel the portion of the playback signal that arrives at the reference microphone.
Therefore, it would be desirable to provide a personal audio device, including a wireless telephone that provides noise cancellation that is effective and/or does not generate undesirable responses when leakage is present from the output transducer to the reference microphone.